Valve having spool assembly with insert divider

ABSTRACT

A spool assembly is disclosed for use in a valve. The spool assembly may have a cylindrical body that is hollow and has a least one radially oriented orifice that passes through a wall of the cylindrical body. The spool assembly may also have an insert slidably disposed inside the cylindrical body. The insert may have a land that axially divides a space inside the cylindrical body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 62/187,907, entitled “VALVE HAVING SPOOL ASSEMBLY WITHINSERT DIVIDER,” and filed on Jul. 2, 2015.

TECHNICAL FIELD

The present disclosure relates generally to a valve and, moreparticularly, to a valve having a spool assembly with an insert divider.

BACKGROUND

Hydraulic machines such as dozers, loaders, excavators, backhoes, motorgraders, and other types of heavy equipment use one or more hydraulicactuators to accomplish a variety of tasks. These actuators are fluidlyconnected to a pump of the machine that provides pressurized fluid tochambers within the actuators, and also connected to a sump of themachine that receives low-pressure fluid discharged from the chambers ofthe actuators. As the fluid moves through the chambers, the pressure ofthe fluid acts on hydraulic surfaces of the chambers to affect movementof the actuators. A flow rate of fluid through the actuators correspondsto a velocity of the actuators, while a pressure differential across theactuators corresponds to a force of the actuators.

Control over the speed and/or force of hydraulic actuators can beprovided by way of one or more metering valves. For example, a firstmetering valve controls fluid flow into a head-end of a hydrauliccylinder, while a second metering valve controls fluid flow out of thehead-end. Likewise, a third metering valve controls fluid flow into arod-end of the hydraulic cylinder, while a fourth metering valvecontrols fluid flow out of the rod-end. The different metering valvesare cooperatively opened and closed (e.g., based on operator input) tocause fluid to flow into one end of the hydraulic cylinder andsimultaneously out of an opposing end, thereby extending or retractingthe hydraulic cylinder.

A conventional metering valve includes a body having a bore thatreceives a spool, and two or more passages formed in the body thatcommunicate with each other via the spool. The spool is generallycylindrical, and includes lands that extend outward away from the bodyon either side of a valley. When the lands are positioned at one or moreentrances of the passages, the spool is in a flow-blocking position.When the spool is moved to a flow-passing position, the valley extendsover the entrances such that fluid communication between the passages isestablished via the valley.

Although conventional spools are acceptable in many applications, theycan be massive and require a significant amount of energy to move thembetween the flow-blocking and flow-passing positions. In addition,because of their mass, the movements of the spools can be slow, causingthe associated hydraulic system to be less responsive than desired. Thelack of responsiveness caused by the spools may require the use ofadditional hydraulic components (e.g., mechanical and/orhydro-mechanical compensators) to offset the effects of the slow spools.

One attempt to improve hydraulic system responsiveness is disclosed in atechnical paper titled “FLOW FORCES ANALYSIS OF AN OPEN CENTER HYDRAULICDIRECTIONAL CONTROL VALVE SLIDING SPOOL” written by R. Amirante et al.that published in the Energy Conversion and Management journal in 2006(“the technical paper”). In particular, the technical paper discloses ahollow spool disposed in the bore of a valve body. The valve bodydefines a tank port, a pump port, a first work port, and a second workport all in communication with the bore. The hollow spool includes fourpatterns of radial orifices, wherein two of the patterns are located ata first end of the hollow spool and associated with the first work port,and two of the patterns are located at a second end and associated withthe second work port. The two ends of the hollow spool are internallyisolated by a block, such that the two ends do not fluidly communicatewith each other. The hollow spool is moved between on- andoff-positions. In a first on-position, the radial orifices in the firstend of the spool connect the first work port with the pump port via thehollow interior of the spool, while the radial orifices in the secondend of the spool connect the second work port with the tank port via thehollow interior of the spool. In a second on-position, the radialorifices in the second end of the spool connect the second work portwith pump port via the hollow interior of the spool, while the radialorifices in the first end of the spool connect the first work port withthe tank port via the hollow interior of the spool. The hollow spool iscenter-biased by way of springs to an off-position, at which the firstand second work ports are not fluidly connected with either of the pumpor tank ports.

Although the hollow spool described in the technical paper may havereduced mass and, therefore, improved responsiveness, it may still beless than optimal. In particular, the integral block formed inside thehollow spool between the first and second ends moves with the hollowspool during valve actuation. As a result, the block axially displacesoil from the valve body during each movement. This displacement of oilmay require a significant amount of energy, and still result in somesystem delay.

The disclosed valve and spool are directed to overcoming one or more ofthe problems set forth above and/or other problems of the prior art.

SUMMARY

One aspect of the present disclosure is directed to a spool assembly fora valve. The spool assembly may include a cylindrical body that ishollow and has a least one radially oriented orifice that passes througha wall of the cylindrical body. The spool assembly may also include aninsert slidably disposed inside the cylindrical body. The insert mayhave a land that axially divides a space inside the cylindrical body.

Another aspect of the present disclosure is directed to a valve. Thevalve may include a block having a bore, a first passage extending tothe bore at a first axial location, and a second passage extending tothe bore at a second axial location. The valve may also include a spoolassembly disposed within the bore of the block. The spool assembly mayinclude a cylindrical body that is hollow and has a least a firstradially oriented orifice that passes through a wall of the cylindricalbody to communicate with the first passage, and at least a secondradially oriented orifice that passes through the wall of thecylindrical body to communicate with the second passage. The spoolassembly may also include an insert slidably disposed inside thecylindrical body and fixedly connected to the block. The insert may havea first land located at a first end adjacent the at least a firstradially oriented orifice, and a second land located at a second endadjacent the at least a second radially oriented orifice. The valve mayfurther include an actuator configured to move the cylindrical body ofthe spool assembly relative to the block and the insert.

Another aspect of the present disclosure is directed to a hydrauliccircuit. The hydraulic circuit may include an actuator, a pump, a sump,and a valve disposed between the actuator, the pump, and the sump. Thevalve may include a valve body having a bore with a first end and asecond end, a first passage formed adjacent the first end incommunication with the bore and in communication with the actuator, asecond passage formed adjacent the second end in communication with thebore and in communication with one of the pump and the sump, and atapered seat located between the first and second passages. The valvemay also include a spool assembly disposed within the bore of the block.The spool assembly may include a cylindrical body that is hollow and hasa least a first radially oriented orifice that passes through a wall ofthe cylindrical body to communicate with the first passage and at leasta second radially oriented orifice that passes through the wall of thecylindrical body to communicate with the second passage. The spoolassembly may also include an insert slidably disposed inside thecylindrical body and fixedly connected to the block. The insert may havea first land located at a first end adjacent the at least a firstradially oriented orifice and a second land located at a second endadjacent the at least a second radially oriented orifice. The spoolassembly may further include a valve actuator connected to the block andconfigured to move the cylindrical body of the spool assembly relativeto the block and the insert.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of an exemplary hydraulic circuit;

FIGS. 2A and 2B are cross-sectional illustration of an exemplarydisclosed valve that may be used in conjunction with the hydrauliccircuit of FIG. 1;

FIG. 3 is an isometric exploded view illustration of an exemplarydisclosed spool that may be used in conjunction with the valve of FIGS.2A and 2B; and

FIG. 4 is a diagrammatic illustration of the spool of FIG. 3.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary hydraulic circuit 10 having at least onetool actuator 12 that is movable based on input received from anoperator. In the disclosed embodiment, two actuators 12 are shown thatare arranged to operate in tandem. These tool actuators 12 are linearactuators (e.g., cylinders) that are commonly used to raise and lowerthe boom of a construction machine (e.g., an excavator—not shown). It iscontemplated, however, that any number of tool actuators 12 could beincluded in hydraulic circuit 10, and embody linear or rotary actuators,as desired. Hydraulic circuit 10 may further include a pump 14configured to draw low-pressure fluid from a sump 16, to pressurize thefluid, and to direct the pressurized fluid through a valve 18 to toolactuators 12. Valve 18, as will be described in more detail below, maybe selectively energized by a controller 20 in response to operatorinput received via an interface device 22 to regulate a flow direction,a flow rate, and/or a pressure of fluid communicated with tool actuators12.

Tool actuators 12, as hydraulic cylinders, may each include a tube 24and a piston assembly 26 arranged within tube 24 to form a first chamber28 and an opposing second chamber 30. In one example, a rod portion ofpiston assembly 26 may extend through an end of first chamber 28. Assuch, first chamber 28 may be considered the rod-end chamber of toolactuator 12, while second chamber 30 may be considered the head-endchamber. Chambers 28, 30 may each be selectively supplied withpressurized fluid and drained of the pressurized fluid to cause pistonassembly 26 to displace within tube 24, thereby changing an effectivelength of tool actuator 12.

It should be noted that, in embodiments where tool actuator 12 is arotary actuator, the configuration and operation of tool actuator 12would be similar to that described above for a linear actuator. Forexample, as a hydraulic motor, tool actuator 12 would include twochambers separated by an impeller. One of these chambers would beselectively supplied with pressurized fluid while the remaining chamberwould be drained of fluid to thereby generate a pressure differentialthat causes the impeller to rotate. The particular chamber filled withfluid or drained of fluid may dictate the rotational direction of theactuator, while the pressure differential and flow rate may dictate theactuation force and speed, respectively.

Pump 14 may be fluidly connected to sump 16 by way of suction passage32, and to valve 18 via a pressure passage 34. In some embodiments, acheck valve 36 may be disposed in pressure passage 34 to help ensure aunidirectional flow of fluid from pump 14 to valve 18. Pump 14 may beany type of pump known in the art, for example a fixed or variabledisplacement piston pump, gear pump, or centrifugal pump. Pump 14 may bedriven by an engine, by an electric motor, or by any other suitablepower source.

Sump 16 may be connected to valve 18 via a drain passage 38. Sump 16 mayconstitute a reservoir configured to hold the low-pressure supply offluid. The fluid may include, for example, a dedicated hydraulic oil, anengine lubrication oil, a transmission lubrication oil, or any otherfluid known in the art. One or more hydraulic circuits may draw fluidfrom and return fluid to sump 16. It is contemplated that hydrauliccircuit 10 could be connected to multiple separate sumps 16 or to asingle sump 16, as desired. A relief valve (not shown) could beassociated with drain passage 38, if desired, to help maintain a desiredpressure within hydraulic circuit 10.

Valve 18 may fluidly communicate with tool actuators 12 via head- androd-end passages 40, 42, and selective pressurization of passages 40, 42may cause desired actuator movements. For example, to retract toolactuators 12, rod-end passage 42 may be filled with fluid pressurized bypump 14 (i.e., passage 42 may be connected with passage 34), whilehead-end passage 40 may be drained of fluid (i.e., passage 40 may beconnected with passage 38). In contrast, to extend tool actuators 12,head-end passage 40 may be filed with fluid pressurized by pump 14,while rod-end passage 42 may be drained of fluid. Valve 18 mayfacilitate these connections.

In the disclosed example, valve 18 is electro-hydraulically operated.Specifically, valve 18 may be selectively energized to cause associatedelements to move between different positions that generate correspondingpilot signals (i.e., flows of pilot fluid). The pilot fluid may flowfrom a pilot pump 44 through a pilot passage 46 to valve 18, and causethe connections described above to be made. In other embodiments,however, valve 18 could be a purely hydraulically-operated valve or apurely electrically operated valve, if desired. In these latterembodiments, pilot pump 44 and pilot passage 46 would be omitted.

As shown in FIGS. 2A and 2B, valve 18 may consist of at least threeprimary components, including a valve block 48, a spool assembly 50disposed in valve block 48, and a valve actuator 52 mounted to valveblock 48 and configured to move portions of spool assembly 50. It shouldbe noted that FIGS. 2A and 2B illustrate only one exemplary embodimentof valve 18 that could be used to control fluid flow into either ofhead-end or rod-end passages 40, 42, or fluid flow out of either ofhead-end or rod-end passages 40, 42. In particular, the embodiment ofvalve 18 shown in FIGS. 2A and 2B could be associated with only thehead-end of tool actuator 12 or only the rod-end, and could function toonly supply fluid to tool actuator 12 or to only drain fluid away fromtool actuator 12. Accordingly, hydraulic circuit 10 (referring toFIG. 1) could have four of the same valves 18 that are shown in FIGS. 2Aand 2B to provide for the full functionality of tool actuators 12 or,alternatively, hydraulic circuit 10 could have the one valve 18 shown inFIGS. 2A and 2B and up to three other valves that are not shown. In thedisclosed embodiment, valve 18 includes a single common valve block 48(see FIG. 1), as well as four separate spool assemblies 50 and fourseparate valve actuators 52 that are connected to the same valve block48. In other embodiments, however, each spool assembly 50 and valveactuator 52 could be associated with a separate valve block 48. Ifmultiple valve blocks 48 are included, they may be bolted together orconnected to each other via conduits.

Valve block 48 may have a bore 54 formed therein for each spool assembly50 that is housed in valve block 48. Bore 54 may have a central axis 56,and extend from a first end 58 to a second end 60 along axis 56. A firstpassage 62 may be formed adjacent first end 58 that intersects with(i.e., is in fluid communication with) bore 54, and a second passage 64may be formed adjacent second end 60 that also intersects with bore 54.In general, first and second passages 62, 64 may be oriented withinvalve block 48 generally orthogonal to central axis 56, and spaced apartfrom each other in an axial direction of bore 54. In the disclosedembodiment, bore 54 may be enlarged at first and second passages 62, 64such that, when spool assembly 50 is disposed inside of bore 54, each ofpassage 62, 64 may communicate with an entire periphery of spoolassembly 50 at the enlarged locations.

A portion of spool assembly 50 may be movable inside bore 54 along axis56 to selectively connect or block fluid flow between first and secondpassages 62, 64. As shown in FIGS. 2 and 3, spool assembly 50 mayinclude, among other things, an elongated cylindrical body (“body”) 66that is hollow, and an insert 68 that is disposed inside body 66. Insert68 may be fixedly connected to block 48, while body 66 may be configuredto slide in an axial direction relative to block 48 and insert 68. Aswill be explained in more detail below, as body 66 slides relative toblock 48, first passage 62 may either be blocked from or connected tosecond passage 64. In one embodiment, a radial clearance between anouter surface of body 66 and an inner surface of bore 54 may be smallenough to inhibit fluid leakage. In other embodiments, however, body 66may include an annular seal (e.g., an o-ring 69) to inhibit the leakage.

Body 66 may include a first open end 70, a second open end 72, and aninternal bore 74 that passes from first open end 70 to second open end72. Internal bore 74, in the disclosed embodiment, has a substantiallyconsistent internal diameter along its length (i.e., no intentionalrestrictions are located inside bore 74). A plurality of radial orifices76 may be formed in body 66 that extend completely through an annularwall 77. Orifices 76 may be arranged into multiple different groupings,and each grouping may be spaced axially-apart from an adjacent groupingand associated with a different passage in block 48. For example, twogroupings 78, 80 are shown in FIGS. 2 and 3 that correspond to thenumber of passages (i.e., first and second passages 62, 64) that need tobe interconnected by spool assembly 50. The orifices 76 within eachseparate grouping 78, 80 may be located at a common axial position, andhave the same diameter and shape or different diameters and shapes, asdesired. In the disclosed embodiment, orifices 76 may be circulardrillings or milled slots, and a combined flow area of all orifices 76within any one of groupings 78 or 80 may be about the same or greaterthan a flow area of the corresponding passage 62 or 64. Any number oforifices 76 may be included within each grouping and spaced around acircumference of body 66 in any manner (e.g., equally or unequally).

Insert 68 may include a stem 82, and a plurality of lands that areaxially spaced apart along stem 82. In the disclosed embodiment, insert68 includes two dividing lands 84, 86 and one mounting land 88, all ofwhich are connected to each other (e.g., via welding, threadedfastening, casting, forging, machining, etc.). It is contemplated thatinsert 68 may have any number of dividing and mounting lands connectedto stem 82. Each of dividing lands 84, 86 and mounting land 88 may begenerally disk-shaped, while stem 82 may be generally rod-like. It iscontemplated that stem 82 may be one continuous rod that passescompletely through dividing land 86, that stem 82 may comprise multiplerod segments joined to each other via dividing land 86, or that stem andone or more of the lands are integrally formed as a single component.Stem 82 may have a generally consistent cross-sectional shape (e.g.,circular) and outer diameter, and the outer diameter may be much smallerthan (e.g., ⅓^(rd) to 1/10^(th) of) a diameter of dividing lands 84, 86.It is contemplated, however, that stem 82 could flare radially outwardat any one or more of the lands, if desired. In an embodiment, themounting land 88 can comprise or be replaced by a pin, a sphericaljoint, a snap ring, or any combination thereof.

Dividing lands 84, 86 may each be configured to divide and/or isolateaxial spaces inside bore 74 of body 66. For example, dividing land 84may be located adjacent orifice grouping 78, while dividing land 84 maybe located adjacent orifice grouping 80 to thereby define an isolatedcylindrical space inside bore 74. In this example, all orifices 76 arelocated between dividing lands 84, 86 (i.e., in communication with thecylindrical space), and dividing lands 84, 86 are configured to containthe fluid being communicated between passages 62, 64 inside bore 74.Lands 84, 86 may inhibit fluid leakage in an axial direction out throughfirst and second open ends 70, 72 of body 66. In one embodiment, aradial clearance between an outer edge of lands 84, 86 and an innersurface of wall 77 may be small enough to inhibit fluid leakage. Inother embodiments, however, one or both of lands 84, 86 may include anannular seal (e.g., an o-ring 89 is shown in FIG. 3 at only dividingland 84) to inhibit the leakage.

Mounting land 88 may be larger than (e.g., have a larger diameter and/orthickness than) dividing lands 84, 86, and be used to connect insert 68to block 48. In particular, mounting land 88 may remain outside of body66 at the second end, and be sandwiched between block 48 and an end cap90 (shown in FIG. 2). In some embodiments, a seal (e.g., an o-ring 92)may be located between an inner surface of mounting land 88 and an outersurface of block 48. It should be noted that insert 68 may be axiallyaligned inside body 66 by way of lands 84 and 86, and only looselyfitted to cap 90. This alignment feature may reduce the tolerancesnormally required for a spool-type valve.

A feedback element 94 may be used to connect body 66 to actuator 52(referring to FIGS. 2A and 2B). In the disclosed embodiment, feedbackelement 94 is a generally solid cylinder connected to first open end 70in such a way that first open end 70 remains substantially open. Forexample, feedback element 94 may have a smaller outer diameter than body66, be axially aligned with body 66, and connect to body 66 by way of aplurality of spokes 96 (see FIG. 4) that extend radially between body 66and the proximal end of feedback element 94. In this configuration anannular spacing 98 between spokes 96 may be still be open.

As discussed above, valve actuator 52, in the disclosed example, is anelectro-hydraulic type of actuator. In particular, valve actuator 52 maybe selectively energized to communicate pilot signals with the end ofspool assembly 50 (e.g., with the distal end 93 of feedback element 94)that cause spool assembly 50 to move between open (i.e., flow passing)and closed (i.e., flow-blocking) positions. When spool assembly 50 is inthe open position (shown in FIG. 2B), grouping 78 of orifices 76 may bein communication with first passage 62 and grouping 80 of orifices 76may be in communication with second passage 64, such that fluid may flowbetween passages 62, 64 via orifices 76 and bore 74. In contrast, whenspool assembly 50 is in the closed-position (shown in FIG. 2A), orifices76 may be blocked from communication with passages 62, 64 by block 48.It should be noted that, although a specific embodiment of valveactuator 52 is shown in FIGS. 2A and 2B, other types of valve actuatorscould alternatively be included in valve 18.

In the exemplary embodiment of FIGS. 2A and 2B, valve actuator 52includes an actuator housing 102 having a bore 104 formed therein thatis in general alignment with bore 54 of valve block 48. Actuator housing102 may be connected to an end of valve block 48, and a seal (e.g., ano-ring 106) may be located therebetween and around bores 54 and 104.Feedback element 94 may be reciprocatingly disposed within bore 104 andextend into bore 54 to connect with body 66. A first pilot supplypassage 108 and a pilot drain passage 110 may be located in housing 102,and configured to communicate pilot pump 44 (e.g., via passage46—referring to FIG. 1) and sump 16, respectively, with the distal end93 of feedback element 94. A solenoid 112 may be connected to housing102 at the outer end, and include a plunger (not shown) that iselectromagnetically movable within an orifice cage 114 to selectivelyconnect one of first pilot supply and pilot drain passages 108, 110 withbore 104. A first spring 116 may extend between the plunger and thedistal end 93 of feedback element 94, and function to provide forcefeedback when solenoid 112 is energized and valve 18 is open. A secondspring 118 may be located between the first end 58 of body 66 and ashoulder of bore 104, and function to close valve 18 when solenoid 112is de-energized.

Controller 20 (referring to FIG. 1) may embody a single microprocessoror multiple microprocessors that include a means for monitoring operatorinput and responsively adjusting flow directions and/or pressures withinhydraulic circuit 10. For example, controller 20 may include a memory, asecondary storage device, a clock, and a processor, such as a centralprocessing unit or any other means for accomplishing a task consistentwith the present disclosure. Numerous commercially availablemicroprocessors can be configured to perform the functions of controller20. It should be appreciated that controller 20 could readily embody ageneral machine controller capable of controlling numerous other machinefunctions. Various other known circuits may be associated withcontroller 20, including signal-conditioning circuitry, communicationcircuitry, and other appropriate circuitry. Controller 20 may be furthercommunicatively coupled with an external computer system, instead of orin addition to including a computer system, as desired.

In some embodiments, controller 20 may rely on sensory information whenregulating the flow directions and/or pressures within hydraulic circuit10. For example, instead of or in addition to the signals generated byinterface device 22, controller 20 may communicate with one or moresensors (not shown) to detect actual pressures inside hydraulic circuit10. These sensors could be mounted in valve block 48 and/or housing 102,if desired. Controller 20 may then automatically adjust flow directionsand/or pressures based on the signals generated by the sensors.

Interface device 22 may embody, for example, a single or multi-axisjoystick located proximal an operator seat (not shown). Interface device22 may be a proportional device configured to position and/or orient awork tool (not shown) by producing signals that are indicative of adesired work tool speed and/or force in a particular direction. Theposition signals may be used by controller 20 to cause correspondingmovements of tool actuator 12 (e.g., by selectively energizing actuator52). It is contemplated that different interface devices 22 mayadditionally or alternatively be included in hydraulic circuit 10 suchas, for example, wheels, knobs, push-pull devices, switches, pedals, andother operator input devices known in the art.

INDUSTRIAL APPLICABILITY

The disclosed valve and spool assembly may be applicable to anyhydraulic circuit. The disclosed valve and spool assembly may providehigh-performance control of a tool actuator in a low-cost and low-weightconfiguration. Control over movement of tool actuator 12 will now bedescribed in detail with reference to FIGS. 1 and 2.

During operation of hydraulic circuit 10 (referring to FIG. 1), pump 14may be driven to pressurize fluid. The pressurized fluid may be directedpast check valve 36 to valve 18 via pressure passage 34. At this sametime, pilot fluid may be pressurized by pilot pump 44 and directed tovalve 18 via pilot supply passage 46. An operator of hydraulic circuit10 may request movement of tool actuator 12 (e.g., extension orretraction) by manipulating (e.g., tilting) interface device 22 in acorresponding direction by a corresponding amount. Electronic signalsgenerated by interface device 22 may be directed to controller 20, whichmay responsively energize or de-energize particular valve actuator(s) 52to achieve the desired tool motion.

During the normal or default state of valve 18, valve actuator 52 may bede-energized. As shown in FIG. 2A, when valve actuator 52 isde-energized, feedback element 94 may be connected to sump 16 via pilotdrain passage 110. At this time, the biasing force of springs 118 mayfunction to urge body 66 of spool assembly 50 downward (relative to theperspective of FIG. 2A), such that all orifices 76 are blocked by theinner block wall of bore 54. In this state, first and second passages62, 64 may be inhibited from communicating with each other via bore 74of body 66.

When valve actuator 52 is energized, the plunger inside of orifice cage114 may be moved upward to communicate pilot supply passage 108 with thedistal end 93 of feedback element 94. This communication may result in apressure imbalance across body 66 of spool assembly 50 that causes body66 to be pushed upward (shown in FIG. 2B). As body 66 moves upward,orifices 76 of grouping 78 may be aligned with first passage 62 at thesame time that orifices 76 of grouping 80 are aligned with secondpassage 64, thereby initiating communication between first and secondpassages 62, 64 via bore 74. In one example, this could result inpressurized fluid flowing into one of head- and rod-end chambers 28 or30 of tool actuator 12 from pump 14. In another example, this couldresult in the draining of one of head- and rod-end chambers 28 or 30 oftool actuator 12 into sump 16. As body 66 moves further upward, agreater flow area of orifices 76 may be uncovered, allowing for agreater flow rate of fluid being communicated between first and secondpassages 62, 64 and a corresponding greater velocity of tool actuator12.

Several benefits may be associated with the disclosed valve and spoolassembly. In particular, because body 66 of spool assembly 50 may behollow and without any restrictions or blockages to axial flow, body 66may be lightweight and displace little fluid during its axial movement.This may reduce a force required to move body 66, which may result inincreased responsiveness of valve 18.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed spool assemblyand valve. Other embodiments will be apparent to those skilled in theart from consideration of the specification and practice of thedisclosed spool assembly and valve. It is intended that thespecification and examples be considered as exemplary only, with a truescope being indicated by the following claims and their equivalents.

What is claimed is:
 1. A valve, comprising: a block having: a bore; afirst passage extending to the bore at a first axial location; and asecond passage extending to the bore at a second axial location; a spoolassembly disposed within the bore of the block and having: a cylindricalbody that is hollow and has a least a first radially oriented orificethat passes through a wall of the cylindrical body to communicate withthe first passage, and at least a second radially oriented orifice thatpasses through the wall of the cylindrical body to communicate with thesecond passage; and an insert slidably disposed inside the cylindricalbody, fixedly connected to the block, and having a first land located ata first end adjacent the at least a first radially oriented orifice anda second land located at a second end adjacent the at least a secondradially oriented orifice; and an actuator configured to move thecylindrical body of the spool assembly relative to the block and theinsert.
 2. The valve of claim 1, wherein the insert has a mounting landformed at one end; and the valve further includes an end cap configuredto close off an end of the bore and to clamp the mounting land to theblock.
 3. The valve of claim 1, further including a feedback elementconnected to an open axial end of the cylindrical body by way of aplurality of spokes, wherein the actuator is an electro-hydraulicactuator configured to selectively communicate a control pressure with adistal end of the feedback element.
 4. The valve of claim 3, furtherincluding: a first spring configured to bias the cylindrical body towarda flow-blocking position; and a second spring configured to bias thefeedback element away from the actuator.
 5. The valve of claim 1,wherein: the at least a first orifice includes a plurality of firstorifices all located at a common first axial position; the at least asecond orifice includes a plurality of second orifices all located at acommon second axial position; the plurality of first orifices and theplurality of second orifices are located axially between the first andsecond lands; and the cylindrical body is open between the first andsecond lands.
 6. A hydraulic circuit, comprising: an actuator; a pump; asump; and a valve disposed between the actuator, the pump, and the sump,the valve including: a block having: a bore with a first end and asecond end; a first passage formed adjacent the first end incommunication with the bore and in communication with the actuator; asecond passage formed adjacent the second end in communication with thebore and in communication with one of the pump and the sump; and a spoolassembly disposed within the bore of the block and having: a cylindricalbody that is hollow and has a least a first radially oriented orificethat passes through a wall of the cylindrical body to communicate withthe first passage and at least a second radially oriented orifice thatpasses through the wall of the cylindrical body to communicate with thesecond passage; and an insert slidably disposed inside the cylindricalbody, fixedly connected to the block, and having a first land located ata first end adjacent the at least a first radially oriented orifice anda second land located at a second end adjacent the at least a secondradially oriented orifice; and a valve actuator connected to the blockand configured to move the cylindrical body of the spool assemblyrelative to the block and the insert.